Turpentine - Varnish Cache

Turpentine - Varnish Cache

Turpentine is a full page cache extension for Magento that works with Varnish, a very fast caching reverse-proxy. By default, Varnish doesn't cache requests with cookies and Magento sends the frontend cookie with every request causing a (near) zero hit-rate for Varnish's cache. Turpentine configures Varnish to work with Magento and modifies Magento's behaviour to significantly improve the cache hit rate.

Note that while this extension is now considered stable, it is strongly recommended that it be tested on a development/staging site before deploying on a production site due to the potential need to add custom ESI policies for blocks added by other extensions.

Features

Full Page Caching, with hole-punching via Varnish ESI and/or AJAX, even for logged in visitors

Requirements

Installation & Usage

Support

If you have an issue, please read the FAQ then if you still need help, open a bug report in GitHub's issue tracker.

Please do not use Magento Connect's Reviews or (especially) the Q&A for support, as it is not monitored as closely as github.

Contributing

If you have a fix or feature for Turpentine, submit a pull request through GitHub to the devel branch. The master branch is only for stable releases. Please make sure the new code follows the same style and conventions as already written code.

How it works

The extension works in two parts, page caching and block (ESI/AJAX) caching. A simplified look at how they work:

For pages, Varnish first checks whether the visitor sent a frontend cookie. If they didn't, then the request will be passed through to Magento in order generate a valid session. Note that the cookie checking is bypassed for clients identified as crawlers (see the Crawler IP Addresses and Crawler User Agents settings).

For blocks, the extension listens for the core_block_abstract_to_html_before event in Magento. When this event is triggered, the extension looks at the block attached to it and if an ESI policy has been defined for the block then the block's template is replaced with a simple ESI (or AJAX) template that tells Varnish to pull the block content from a separate URL. Varnish then does another request to that URL to get the content for that block, which can be cached separately from the page and may differ between different visitors/clients.

Notes and Caveats

Turpentine will not help (directly) with the speed of "actions" like adding things to the cart or checking out. It only caches, so it can only speed up page load speed for site browsing. It will remove a lot of load on the backend though so for heavily loaded sites it can free up enough backend resources to have a noticeable effect on "actions".

There are some technical limitations when using Varnish 2.1.x: External ESI requests are not blocked, and per-block TTLs in ESI policies are not honored (all blocks use the default TTL)

The core parts of Turpentine (caching and ESI/AJAX injection) work under Magento CE 1.5, but a significant portion of the auxillary functionality doesn't work due to changes to event names. That said, it would be possible to use Turpentine with Magento CE 1.5 with an understanding that it is not supported and what actions need to be taken manually. Both cache flushing (both automatic an manual) and cache warming (due to missing events that trigger the cache flushing) do not work.

Anonymous blocks are not able to be hole-punched. For CMS pages, it is recommended that you include the block in the page's layout updates XML and give it a name, then it can have an ESI policy like normal

Known Issues

Logging and statistics will show all requests as coming from the same IP address (usually localhost/127.0.0.1). It should be possible to work around this using Apache's mod_remoteip or mod_rpaf.